10 years later: A proven methodology for nearly zero energy buildings
Authors
A decade ago, I had the opportunity to present at a conference for zero energy buildings, outlining a working methodology for designing highly energy-efficient buildings. At the time, the concept of nearly zero energy, or even zero energy buildings was still evolving, with regulatory definitions often failing to capture the full scope of energy consumption in buildings. The approach I presented was based on a multidisciplinary strategy that prioritised passive design, energy efficiency, and integrated renewable energy solutions.
Looking back now, ten years later, not only has the methodology stood the test of time but has proven to be even more relevant as we face increasingly urgent climate challenges and stricter energy regulations. Our focus at Cundall, particularly in the Spanish market, has been on sustainable design and energy optimisation of buildings. This has allowed us to apply and refine these principles in active projects, demonstrating that the step-by-step approach outlined in my presentation remains highly effective.
A methodology that works
The core idea I presented was simple yet powerful: reducing energy consumption must come before introducing renewable energy sources. This is achieved through a structured process:
- Reevaluating design assumptions – questioning unnecessary energy intensive features, such as excessive glazing and rigid temperature controls, to optimise building performance from the start.
- Passive design strategies – leveraging natural ventilation, thermal mass, and solar shading to reduce cooling and heating loads.
- Energy efficiency measures – incorporating high-performance equipment, LED lighting, and intelligent controls to minimise operational energy use.
- Energy recovery solutions – using heat recovery, adiabatic cooling, and other techniques to maximise efficiency.
- On-site renewable integration – only after minimising demand does it make sense to introduce photovoltaic panels and other renewable systems.
By following these steps, we demonstrated how a standard office building could reduce energy consumption by up to 87%, making the transition to a nearly zero energy building both practical and cost effective.
The present and future of nZEBs
Fast forward to today, and the importance of this approach has only grown. Energy efficiency is now at the heart of sustainable building design, driven by both regulatory frameworks like the European Energy Performance of Buildings Directive, the recent Taxonomy requirements and the increasing urgency of carbon reduction targets.
Additionally, advances in building technologies, such as AI-driven energy management and new materials with enhanced thermal properties, have further strengthened the effectiveness of our methodology. However, the core principles remain unchanged: a holistic, integrated approach is the key to designing truly sustainable buildings.
Why this matters now
As we strive towards net zero carbon goals, the conversation has shifted from energy consumption alone to the embodied carbon of materials and the lifecycle impact of buildings. The methodology presented ten years ago was ahead of its time in considering a building’s total energy profile, not just operational efficiency. This perspective is now crucial as we move towards circular economy principles and climate-resilient design.
The video from my presentation remains a valuable resource, illustrating the foundation of an approach that has become more relevant. I invite you to watch it and see how these principles continue to shape the future of sustainable design.
Let’s continue pushing the boundaries of what is possible in energy efficient building design - because now, more than ever, we need solutions that work.
This video was originally recorded at the 3rd Nearly Zero Energy Buildings Congress and is the intellectual property of Grupo Tecma Red S.L., published on CONSTRUIBLE. Used with permission. Original source: José Castilla, Cundall España - III Congreso EECN • CONSTRUIBLE,14 July 2016.
